I think most "junk" you see in loops is from users not using a biocide or cheap tubing leeching plasticizers. Some dye additives can cause problems. Flush your blocks and rads, use distilled water and biocide you should not need a filter.
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thanks madcratebuilder ..............so far , what I have researched on the subject in various threads , I do fully agree with you..
I would like to meet the objective opinion of Shoggy ( and anyone who wants to give it ) ; although Shoggy may seem like a "partial" person in that opinión , I trust your judgment and professionalism